Thermally developable lightsensitive elements

ABSTRACT

A THERMALLY DEVELOPABLE LIGHT-SENSITIVE ELEMENT COMPRISING A SUPPORT BEARING, AT LEAST ONE LAYER CONTAINING AT LEAST (A) A LIGHT INSENSITIVE AND REDUCIBLE ORGANIC SILIVER SALT, (B) AT LEAST ONE MEMBER SELECTED FROM THE GROUP CONSISTING OF A SILVER HALIDE AND AN INORGANIC HALIDE CAPABLE OF FORMING A SILVER HALIDE BY THE REACTION THEREOF WITH SAID ORGANIC SILVER SALT (A), AND (C) A REDUCING MATERIAL CAPABLE OF BEING DECOMPOSED BY THE IRRADIATION WITH ACTINIC RADIATION TO LOSE ITS REDUCING PROPERTIES, WHICH CONTACTS AT LEAST ONE MATERIAL CAPABLE OF ACCELERATING THE DECOMPOSITION OF THE REDUCING MATERIAL BY IRRADIATION WITH ACTINIC RADIATION IN AT LEAST ONE LAYER THEREOF.

. g States Patent Olfice 3,75%,829 Patented Sept. 4, 1973 ,3 int. Cl.G03c 1/02, 1/76, 3/00 ILS. Cl. 96-4141 11 (Ilaims ABSTRACT OF THEDISCLOSURE A thermally developable light-sensitive element comprising asupport hearing, at least one layer containing at least (a) a lightinsensitive and reducible organic silver salt, (b) at least one memberselected from the group consisting of a silver halide and an inorganichalide capable of forming a silver halide by the reaction thereof withsaid organic silver salt (a), and (c) a reducing material capable ofbeing decomposed by the irradiation with actinic radiation to lose itsreducing properties, which contacts at least one material capable ofaccelerating the decomposition of the reducing material by irradiationwith actinic radiation in at least one layer thereof.

BACKGROUND OF THE INVENTION (1) Field of the invention The presentinvention relates to a thermally developable light-sensitive element andmore particularly, to a thermally developable light-sensitive elementcontaining, as a reducing agent, a compound capable of being decomposedby irradiation with actinic rays, and a compound capable of acceleratingthe decomposition of the reducing agent by irradiation with actinicrays. 'lhe invention also relates to copying processes using suchelements.

(2) Description of the prior art In general, a photographiclight-sensitive element in which a silver halide is used has been mostwidely employed as a light-sensitive element, since such a photographicsilver halide light-sensitive element is excellent in sensitivity andgradation as compared with electrophotographic light-sensitive elementsand other photographic light-sensitive elements.

However, in this photographic silver halide light-sensitive element,there are such difficulties that the lightsensitive element must besubjected to several processing steps, that is, stopping, fixing, andstabilizing in order to prevent the developed image from becomingdiscolored or faded and also to prevent the background thereof frombeing blackened.

Therefore, it is very desirable to obtain light-sensitive elements whichcan be easily fixed or stabilized after development.

The inventors have previously providied, as the aforesaidlight-sensitive element including a simple stabilization processing, athermally developable light-sensitive element comprising a supporthearing at least one layer containing at least (a) a light insensitiveand reducible organic silver salt, (b) a silver halide or an inorganichalide capable of forming a light-sensitive silver halide by thereaction with the organic silver salt (a), and (c) a developing agent ora reducing material capable of being decomposed by the irradiation ofactinic rays to lose its reducing properties.

When the thermally developable light-sensitive element as mentionedabove is exposed to an incandescent tungsten lamp in the usual mannerand then developed by heating, the light exposed portions are blackenedto provide photographic images. When the light-sensitive element thusdeveloped is placed in the light, the reducing material (that is, thedeveloping agent) is decomposed by the action of actinic rays includedin sunlight or light from an ultraviolet lamp to lose its reducingproperties. In other Words, the light-sensitive element which has beenleft in the light after exposure and development provides stabilizedreproductions or images which are not to be developed any more in thelight exposed portions even by heating again. That is, the aforesaidlight-sensitive element can be fixed by exposure to light. Moreover,when the aforesaid light-senitive element is placed in the light afterdevelopment, it is fixed spontaneously, in other Words, the aforesaidlight-sensitive element requires no fixing processing.

Also, the thermally developable light-sensitive element containing sucha reducing material can be used as an autopositive element. That is,when, after imagewise exposing the thermally developable light-sensitiveelement by actinic rays, the light-sensitive element is slightly exposeduniformly to a tungsten light and then developed by heating, thereducing material at the portions exposed to the actinic rays isdecomposed or loses its reducing properties and hence, the exposedportions will not be developed when the thermally developablelight-sensitive element is heated thereafter. On the other hand, sincethe reducing agent or the developing agent at the portions which havenot been subjected to exposure with actinic rays remains undecomposed,the nonexposed portions will be developed by the subsequent uniformtungsten lamp exposure and heating. Accordingly, it will be understoodthat the thermally developable light-sensitive element containing such areducing material can be used as autopositive light-sensitive elements.

The inventors have found that the light fixing property of the thermallydevelopable light-sensitive element and the sensitivity thereof as anautopositive light-sensitive element can be further improved byincorporating a compound capable of accelerating the decomposition of areducing material by an actinic irradiation in a thermally developablelight-sensitive element containing the reducible material capable ofbeing decomposed by the actinic radiation to lose its reducing power.

Thus, an object of this invention is to provide a thermally developablelight-sensitive element capable of providing both a negative copy and apositive copy of an original according to the kind of light source usedfor exposure.

Another object of this invention is to provide a thermally developablelight-sensitive element having a high sensitivity and capable of beingdeveloped by only heating Without using developing solution and that theimage developed by heating is stabilized to light without beingprocessed by fixing or the like and can be stored substantiallypermanently.

SUMMARY OF THE INVENTION These objects can be attained by incorporatinga compound capable of accelerating the decomposition of a reducingmaterial by the actinic irradiation in the thermally developablelight-sensitive element comprising a support bearing at least one layercontaining at least (a) A light-insensitive and reducible organic silversalt,

(b) A silver halide or an inorganic halide capable of forming alight-sensitive silver halide by the reaction with the light insensitiveorganic silver salt (a), and

(c) A reducing material capable of being decomposed by the irradiationof actinic rays to lose its reducing properties.

That is, by incorporated the compound capable of accelerating thedecomposition of the reducing material by the irradiation of actinicrays in the aforesaid thermally developable light-sensitive element, thelight-sensitive element can be developed by a completely dry process toprovide very stable reproductions or images without fixing or othertroublesome processings. In particular, since the reducing materialcontained in the light sensitive element is easily decomposed by theirradiation of actinic rays according to the present invention, thestability of the images obtained by the thermal development is furtherincreased.

DETAILED DESCRIPTION OF THE INVENTION The light insensitive andreducible silver salt to be used in the present invention may be asilver salt of an organic compound having an imino group, a silver saltof an organic compound having a mercapto group, or a silver salt of anorganic acid. In these silver salts, there are included lightinsensitive silver salts and light-sensitive silver salts. Also, somesilver salts shown highly reducible properties while other silver saltsshow weak reducible properties. Among them, the silver salts suitablefor the present invention are ones having light insensitivity or verylow sensitivity and having high reducible properties.

As examples of silver salts which have been found to be suitable for thepresent invention, there are illustrated a silver salt of1,2,3-benzotriazole, a silver salt of benzosulfimide, a silver salt of3-mercapto-4-phenyl-1,2,4-triazole, a silver salt ofl-phenyl-S-mercapto-tetrazole, a silver salt of4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene, a silver salt of2-(S-ethylthioglycloamido)benzothiazole, a silver salt of myristic acid,a silver salt of lauric acid, a silver salt of palmitic acid, a silversalt of stearic acid, and a silver salt of behenic acid.

The inorganic halide capable of forming a light-sensitive silver halideused in this invention is a compound soluble in water or in an organicsolvent, said compound being represented by the general formula:

wherein M represents a hydrogen atom, ammonium, and a metal (such as,strontium, cadmium, zinc, tin, chromium, sodium barium, iron, cesium,lanthanum, copper, calcium, nickel, magnesium, potassium, aluminum,antimony, gold, cobalt, mercury, lead, and beryllium); X represents ahalogen atom (such as, chlorine, bromine, and iodine); and n is avalence of M.

Among them, the iodides are particularly preferable as the silver saltthereof has the properties that it is difficult to be printed out.

The reducing material in this invention, which can be decomposed by theirradiation of actinic rays to lose its reducing properties is acompound having the group represented by the general formula:

wherein R and R represent a hydrogen atom, an alkyl group, or an acylgroup and n is an integer selected from and 1.

Among the compounds represented by the above general formulae, thesuitable examples for the present invention are illustrated l-ascorbicacid, l-ascorbyl monoester, l-ascorbyl diester, furoin, benzoin,dihydroxyacetone, 1,2-dihydroxynaphthalene, 1,4-dihydroxynaphthalene,4-methoxy-1-naphthol, and 4 ethoxy 1 naphthol. These compounds can bedecomposed by the irradiation of an actinic radiation.

Moreover, as the material used in this invention. which can acceleratethe decomposition of the aforesaid reducing material by the irradiationof an actinic ray, there may be effectively employed a compound capableof forming an excited molecule or a radical by the irradiation ofactinic rays or a dye which is easily decomposed by the irradiation ofactinic rays.

That is, there are the following compounds (1)-(4) capable of formingexcited molecules or radicals by the irradiation of actinic rays anddyes (5) capable of being easily decomposed by the irradiation ofactinic rays. Thus,

(1) Diketones, such as diacetyl or benzil;

(2) Polynuclear aromatic compound, such as anthra cene, fiuorenone, 9,10anthraquinone, 2 chloroanthraquinone, fl-methylanthraquinone;

(3) Metal oxides, such as stannic oxide, cupric oxide, manganese oxide,or magnesium oxide; and

(4) Light-sensitive cerium compound, such as cerium nitrate, 4

(5) Dyes (a) phthalein dyes, such as erythrosine, eosine, and

Rhodamine B,

(b) cyanine dyes, such as 3,3-diethylthiazolinocarbocyanine iodide,1-ethyl-3-propyl 5 [2 (lmethy1-2(1H)-pyrrolinylidene)ethylidene] 2thiohydantoin, and

(c) others, such as Methylene Blue, Methyl Violet,

profiavine, phenosafranine, and Chrysoidine.

The proportion of the above-mentioned material for accelerating thedecomposition of the reducing agent by an actinic irradiation isinfluenced by the combination of the above-mentioned material and thereducing material, but it is preferable to use to 20 parts by weight indiketones (l), to 10 parts by weight in polynuclear aromatic compounds(2), to 10 parts by weight in metal oxides, to 10 parts by weight incerium compounds (4) and to one part by weight in dyes (5) per one partby weight of the reducing material.

If the amount of the material is lower than this proportion, there islittle effect, and if the amount thereof is higher, the shelf life ofunexposed light-sensitive elements will be reduced.

Further, by employing these material in combination, the decompositionaccelerating effect may be increased.

In the case of using the thermally developable lightsensitive elementsof this invention as usual negative working, the light-sensitive elementmay be, after being exposed to a tungsten lamp, developed by onlyheating. On the other hand, the thermally developable light-sensitiveelement of the present invention may be utilized as an autopositivelight-sensitive element. That is, after exposing the thermallydevelopable light-sensitive element to actinic rays imagewise to anextent of decomposition the reducing material contained in thelight-sensitive element, the light-sensitive element thus imagewiseexposed is exposed again uniformly to actinic radiation or light from anincandescent lamp to an extent by which the reducing material is notdecomposed and thereafter is developed by heating, whereby the reducingmaterial at the areas exposed to the first actinic radiation isdecomposed, that is, the developing agent loses its developing power.Thus, when the light-sensitive element is heated thereafter, the exposedarea will not be developed. On the other hand, there remainsundecomposed reducing agent at the areas which had not been irradiatedby the first actinic rays, and hence, by the subsequent uniform weakirradiation of the actinic rays or exposure to the tungsten lampfollowed by heating, the areas where there remained reducing agentundecomposed are developed. Therefore, the thermally developablelight-sensitive element may be utilized as an autopositivelight-sensitive element.

In particular, in the case of the thermally developable light-sensitiveelement of this invention is used as autopositive light-sensitiveelement, the whole processes are conducted by dry systems too. When thewhole process has been conducted, the reducing agent at the image areas,

as well as at the background areas has been decomposed, and then, nomore development proceeds in the lightsensitive element thus developedduring storage. Thus, the light-sensitive element developed will not bediscolored substantially permanently and consequently, the contrastbetween densities of the image areas and the background areas thereofwill be kept high for a long period of time.

In the thermally developable light-sensitive element previously providedby the inventors (see Ser. No. 643,828, filed June 6, 1967) whichcomprises a support hearing at least one layer containing at least (a) alight insensitive and reducible organic silver salt, (b) a silver halideor an inorganic halide capable of forming a lightsensitive silver halideby the reaction with the organic silver salt (a) and (c) a developingagent or a reducing material capable of being decomposed by theirradiation of actinic rays to lose its reducing properties, it tookmore than 5 minutes to decompose the reducing material by irradiatingwith the light from a high pressure mercury lamp of 400 watts thethermally developable light-sensitive element placed with a distance ofcm. from the light source. Accordingly, the previous light-sensitiveelement invented by us is insufliciently used as an autopositivelight-sensitive element. On the other hand, in the thermally developablelight-sensitive element of the present invention containing the materialwhich can accelerate the decomposition of the reducing agent by lightexposure, the reducing agent therein is sufliciently decomposed when thelight-sensitive element is irradiated for one minute by a high pressuremercury lamp of 400 watts a distance of 10 cm. from the light source.The sensitivity of the element has increased as much as four times.Further, with a high pressure mercury lamp of 1200 watts, the reducingagent will be decomposed by the irradiation of -30 seconds.

The thermally developable light-sensitive element of this invention hasthe following advantages:

(1) Excellent in shelf life thereof in the unexposed state.

(2) Excellent in shelf life after processing without necessity ofprocessing such as fixing and stabilizing processing after developmentas the light-sensitive element is stabilized by the irradiation of anactive ray.

(3) Utilization thereof for negative working, as well as for positiveworking.

The invention will be explained practically by the following examplesbut the invention should not be limited to the following examples by anymeans.

EXAMPLE 1 A uniform dispersion having the following composition wasapplied to a paper (per 1 sq. m. thereof) and dried:

"3 ethyl-5-[ (3-methyl-2-thiazolinllidene) ethylidene1-rhodanine (of.;Journal of Physical Chemistry, vol. 56, 1062 (1952).

The dry thickness was 10 microns. The light-sensitive element thusprepared was exposed imagewise to a tungsten lamp and heated to 120 C.for 10 seconds to provide a good negative image. When thelight-sensitive paper thus developed was further exposed to white light,the

contrast between the image areas and the background areas was notvaried.

Another unexposed sample was superposed on a transparent original havingpatterns, the light-sensitive paper was then exposed for one minutethrough the original to a high pressure mercury lamp of 400 watts with adistance of 10 cm. from the light source, and the original was removed.Thereafter, the light-sensitive element thus processed was furtherexposed for a short period of time to a tungsten lamp and heated to C.for 10 seconds to provide a good positive image. Furthermore, anothernew sample of this example was superposed on a transparent original andexposed for 15 seconds through the original to a high pressure mercurylamp of 1200 watts with a distance of 10 cm. from the light source.After removing the original, the light-sensitive element was furtherexposed for a short period of time to a tungsten lamp and then heated to120 C. for 10 seconds to provide a good positive image.

When these light-sensitive papers thus developed were further exposed towhite light, the contrast between the images and the backgrounds was notvaried.

EXAMPLE 2 A uniform dispersion having the following composition wasapplied to a paper (per one sq. m. thereof) and dried to form alight-sensitive layer having a dry thickness of 10 microns:

Polyvinyl butyral (15 wt. percent methanol solution)18 Ascorbylpalmitate0.12 g. Sodium benzenesulfinate0.-06 g. Benzil--0.6 g.

Sebacic acid-2.4 g.

*The same merocyanine dye as in Example 1.

When the light-sensitive paper thus prepared was exposed to a tungstenlamp and heated for 10 minutes to 120 C., a good negative image wasobtained.

Further, another sample, same as above, was superposed on a transparentoriginal and exposed for 20 seconds through the original to a highpressure mercury lamp of 1200 watts with a distance of 10 cm. from thelight source. After removing the transparent original, thelightsensitive paper was exposed again for a short period of time to atungsten lamp and heated for 10 seconds to 120 C. to provide a goodpositive image having a high contrast, which was not varied when thelight-sensitive paper was placed in white light for a long period oftime.

EXAMPLE 3 A uniform dispersion having the following composition wasapplied to a paper (per one sq. m. thereof) and dried to form a layer of10 microns in dry thickness.

Polyvinyl butyral (15 wt. percent methanol solution)- Silver salt ofbenzotriazole (15 wt. percent methanol dispersion)-15 ml.

Potassium iodide (l/SO N methanol sol.)-15 ml.

Sensitizing dye*-(0.25 wt. percent methanol sol.)0.4

After removing the transparent original, the light-sensitive paper wasuniformly exposed to visible light for a short period of time and thenheated to 120 C. for 10 seconds to provide a good positive image withwhite background. When the light-sensitive paper thus developed wasplaced in white light, the contrast between the image and the backgroundwas not varied.

EXAMPLE 4 A uniform dispersion having the following composition wasapplied to a paper and dried to form a layer of 10 microns in drythickness:

Polyvinyl butyral (15 wt. percent methanol solution)- Silver salt ofbenzotriazole (15 wt. percent methanol dispersion)-25 ml.

Potassium iodide (1/50 N methanol sol.)25 ml. Sensitizing dye*(0.25 wt.percent methanol sol.)-0.6

4-methoxy-l-naphthol0.3 g. Sodium benzenesulfinate--0.l g. Manganesedioxide (1 wt. percent methanol dispersion)- Sebacic acid-4.5 g.

*The same merocyanlne dye as in Example 1.

By processing the light-sensitive paper thus prepared as in Example 1, agood negative image which could be fixed by light was obtained and alsoby exposure to ultraviolet rays, a positive image was obained as inExample 1.

EXAMPLE 5 A uniform dispersion having the following composition wasapplied to a paper and dried to form a layer of 10 microns in drythickness:

Polyvinyl butyral (15 wt. percent methanol solution)30 Silver salt ofbenzotriazole (15 wt. percent methanol dispersion)-25 ml.

Potassium iodide (1/50 N methanol solution)25 ml.

Sensitizing dye*(0.25 wt. percent methanol sol.)0.6

3,3'-diethylthiazolinocarbocyanine iodide0.2 g.

Ascorbyl palmitate--0.2 g.

Sodium benzenesulfinate-0.1 g.

Sebacic acid-4.5 g.

*The same merocyanine dye as in Example 1.

By processing the light-sensitive paper as in Example 1, a good negativeimage which could be fixed by light was obtained and also by theexposure to ultraviolet rays, a positive image Was obtained.

EXAMPLE 6 A uniform dispersion having the following composition wasapplied to a paper (per one sq. m.) and dried to form a layer of 10microns in dry thickness.

Polyvinyl butyral (15 wt. percent methanol solution)- Silver salt of6-bromobenzotriazole (15 wt. percent methanol dispersion)25 ml.

Zinc iodide (1.50 N methanol solution)-25 ml.

Sensitizing dye (0.025 wt. percent methanol solution)- Ascorbylstearate-0.4 g.

9,l-Anthraquinone0.6 g.

Sebacic acid4.0 g.

Magnesium oxide wt. percent methanol dispersion) *The same dye as inExample 3.

When the light-sensitive paper thus prepared was exposed to a tungstenlamp and heated for 10 seconds to 120 C., a good negative image wasobtained. Also, another unexposed sample was superposed on a transparentoriginal and exposed for 20 seconds through the original to a highpressure mercury lamp of 1200 watts with a distance of 10 cm. from thelight source. After removing the original therefrom, the light-sensitivepaper was exposed again uniformly to visible light for a short period oftime and heated to C. for 10 seconds to provide a positive image.

EXAMPLE 7 A uniform dispersion having the following composition wasapplied to a paper (per one sq. m.) and dried.

Polyvinyl butyral (15 wt. percent methanol solution)lS Silver salt ofbenzotriazole (15 wt. percent methanol dispersion)-25 ml.

Ascorbyl dipalmitate0.6 g.

Benzil--2.5 g.

Sebacic acid-4.0 g.

To the layer thus formed (per one sq. m.) was applied a uniformdispersion having the following composition and dried:

Polyvinyl butyral (15 wt. percent methanol solution)lS Strontium iodide(l/50 N methanol solution)25 ml.

Sensitizing dye* (0.025 wt. percent methanol solution) The samemerocyanlne dye as in Example 3.

When the light-sensitive paper thus prepared was exposed to a tungstenlamp and heated for 10 seconds to 120 C., a negative image was obtained.Also, the other unexposed sample was superposed on a transparentoriginal and exposed for 30 seconds through the original to a highpressure mercury lamp of 1200 watts with a distance of 10 cm. from thelight source. After removing the original therefrom, the light-sensitivepaper was exposed for a short period of time to a tungsten lamp andheated for 15 seconds to 120 C. to provide a good positive image.

EXAMPLE 8 A uniform dispersion having the following composition wasapplied to a paper (per one sq. m.) and dried:

Polyvinyl butyral (15 wt. percent methanol solution)-30 Silver salt of5-methyl-7-hydroxy-1,3,5-triazaindolizine (15 wt. percent methanoldispersion)25 ml.

Potassium iodide (1/50 N methanol solution)-25 ml.

Sensitizing dye* (0.025 wt. percent methanol solution)1,4-dihydroxynaphthalene-O.6 g.

Diacetyl1.5 g.

Sebacic acid-4.0 g.

*The same merocyanine dye as in Example 1.

When the light sensitive paper thus prepared was exposed to a tungstenlamp and heated for 10 seconds to 120 C., a negative image was obtained.Also, the other unexposed sample was superposed on a transparentoriginal and exposed for 30 seconds to a high pressure mercury lamp of1200 watts with a distance of 10 cm. from the light source. Afterremoving the transparent original, the light-sensitive paper was exposedagain to a tungsten lamp for a short period of time and heated to 120 C.for 10 seconds to provide a good positive image.

What is claimed is:

1. A thermally developable light-sensitive element which is light-stableafter development comprising a support bearing thereon at least onelayer containing at least (a) a light-insensitive and reducible organicsilver salt selected from the group consisting of a silver salt of anorganic compound having an imino group, a silver salt of an organiccompound having a mercapto group and a silver salt of an organic acid;

(b) at least one member selected from the group consisting of a silverhalide and an inorganic halide capable of forming a silver halide by thereaction thereof with said organic silver salt (a);

(c) a reducing material capable of being decomposed by irradiation withactinic radiation to lose its reducing properties, said reducingmaterial being selected from the group consisting of compounds havingthe group represented by the general formula and compounds having thegroup represented by the general formula wherein R and R represent amember selected from the group consisting of a hydrogen atom, an alkylgroup, and an acyl group and wherein n is an integer selected from and1; and

(d) at least one member selected from the group consisting of (1)compounds forming excited molecules or radicals in response toirradiation with actinic radiation and selected from the groupconsisting of (i) diketones selected from the group consisting ofdiacetyl and benzil,

(ii) polynuclear aromatic compounds selected from the group consistingof anthracene, fluorenone, 9,10-anthraquinone, 2-chloroanthraquinone,and fi-methylanthraquinone,

(iii) metal oxides selected from the group consisting of stannic oxide,cupric oxide, manganese oxide and magnesium oxide, and

(iv) cerium nitrate; and

(2) dyes easily decomposed by irradiation with actinic radiationselected from the group consisting of erythrosine, cosine, Rhodamine B,3,3 diethylthiazolino carbocyanine-carbocyanine iodide,1-ethyl-3-propyl-5-(1-methyl-2 (1H) pyrrolinylidene)ethylidene) 2thiohydantoin, Methylene Blue, Methyl Violet, proflavine,phenosafranine, and Chrysoidine; said member being capable ofaccelerating the decomposition of said reducing material by irradiationwith actinic radiation.

2. The thermally developable light-sensitive element according to claim1 wherein said reducing material is selected from the group consistingof l-ascorbic acid, l-ascorbyl monoester, l-ascorbyl diester, furoin,benzoin, dihydroxyacetone, 1,2-dihydroxynaphthalene,1,4-dihydroxynaphthalene, 4-methoxy-1-naphthol, and 4-ethoxyl-naphthol.

3. The thermally developable light-sensitive element according to claim4 wherein said reducing material capable of being decomposed byirradiation with actinic radiation to lose its reducing properties isselected from to group consisting of l-ascorbic acid, l-ascorbylmonoester, l-ascorbyl diester, furoin, benzoin, dihydroxyacetone,1,2-dihydroxynaphthalene, 1,4-dihydroxynaphthalene,4-methoxy-1-naphthol, and 4-ethoxy-1-naphthol.

4. The thermally developable light-sensitive element according to claim1 wherein said silver salt is selected from the group consisting of thesilver salt of benzotriazole, the silver salt of 6-bromobenzotriazoleand the silver salt of 5-methyl-7-hydroxy-1,3,5-triazaindolizine.

5. The thermally developable light-sensitive element according to claim1 wherein said inorganic halide is a metal iodide.

'6. The thermally developable light-sensitive element according to claim2 wherein said inorganic halide is a water-soluble or organicsolvent-soluble compound of the formula: MXn Where M represents ahydrogen atom, an ammonium group or a metal; X represents a halogenatom; and n is thevalence of M.

7. The thermally developable light-sensitive element according to claim6 wherein the metal of said inorganic halide is selected from the groupconsisting of strontium, cadmium, zinc, tin, chromium, sodium, barium,iron, cesium, lanthanum, copper, calcium, nickel, magnesium, potassium,aluminum, antimony, gold, cobalt, mercury, lead, and beryllium.

8. The thermally developable light-sensitive element according to claim3 wherein said inorganic halide is a water-soluble or organicsolvent-soluble compound of the formula: MXn wherein M represents ahydrogen atom, an ammonium group or a metal; X. represents a halogenatom; and n is the valence of M.

9. The thermally developable light-sensitive element according to claim8 wherein said layer consists essentially of said silver salt, at leastone member selected from the group consisting of said silver halide andsaid inorganic halide, said reducing material and said member capable ofaccelerating the decomposition of said reducing material by irradiationwith actinic radiation.

10. A process for obtaining a negative print of an original comprisingexposing imagewise the thermally developable light-sensitive elementdescribed in claim 1 to light from a tungsten lamp and developing byheating to about C.

11. A process for obtaining a positive print of an original comprisingexposing imagewise the thermally developable light-sensitive elementdescribed in claim 1 to actinic radiation from a mercury lamp, thenexposing to light from a tungsten lamp, and developing by heating toabout 120 C.

References Cited UNITED STATES PATENTS 3,526,505 9/1970 Workman 96-11413,529,963 9/ 1970 Marchese 96--114.1 3,152,904 10/1964 Sorenson et al.96-1 14.1 3,409,438 11/1968 Lokken 96-114.1 3,429,706 2/ 1969 Shepard96-114, 1 3,457,075 7/1969 Morgan 96114.1

NORMAN G. TORCHIN, Primary Examiner M. F. KELLEY, Assistant Examiner US.Cl. X.R. 96-67, 68

